#include <Keypad.h>

const uint8_t ROWS = 4;
const uint8_t COLS = 4;
char keys[ROWS][COLS] = {
  { 'A', 'B', 'C', '$' },
  { 'D', 'E', 'F', '*' },
  { 'G', 'H', 'I', 'X' },
  { 'C', 'J', 'B', 'N' }
};

uint8_t colPins[COLS] = { 5, 4, 3, 2 };
uint8_t rowPins[ROWS] = { 9, 8, 7, 6 };

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);
void setup() {
  Serial.begin(9600);
}

void loop() {
  char key = keypad.getKey();
  
  if (key) {
    Serial.println(String(key));
    if (key == 'A') {
      Serial.println("AHA");
    }
  }
  
  delay(100);
}